modified gravity: answer to dark matter/energy?
DESCRIPTION
Modified Gravity: answer to Dark Matter/Energy?. HongSheng Zhao Univ. of St Andrews, UK. Late acceleration+3 rd peak Einstein’s Eq. needs fix. RHS ⇒ Dark energy + DM e.g., Vaccum energy, Chaplygin gas 2. LHS ⇒ Modified gravity - PowerPoint PPT PresentationTRANSCRIPT
Modified Gravity: answer to Dark Matter/Energy?
HongSheng ZhaoUniv. of St Andrews, UK
Late acceleration+3rd peak
Einstein’s Eq. needs fix
1. RHS ⇒ Dark energy + DMe.g., Vaccum energy, Chaplygin gas
2. LHS ⇒ Modified gravity e.g., 1/R gravity (Carroll et al.,
2003) dominates late
Bekenstein’s TeVeS for MOND
a0]2 ~
=0
3
Deflection by φDM ~ φTeVeS
• Galactic Potential = lum+φTeVeS = lum+ φDM
ds2 = (1+2) dt2 - (1-2) ( dx2 + dy2 + dz2 )
• DM + DE --> Baryon-tracking Scalar field
Bekenstein (2004), Angus, Famaey, Zhao (2006)
Need Modified Gravity ~ Dark Matter
Bruneton, Famaey, Gentile, Nipoti, Zhao (2006)
(gDM/glum ).gDM ~ a0~ 1/2
A Fake Hybrid Spiral Galaxy
Scarpa; http://xxx.lanl.gov/pdf/astro-ph/0601478
MOND fails to fit (Good !!) DM fits fine
Stars
GasGas
Stars (with smaller M/L)
++Q- -
- -
+ +
++
▼. [s ▼ φ] = 4Glum = ▼. ▼ Φlum
Matter-tracking Dielectric s ~ ▼φ /a0 , a0 ~ 1/2
Polarisation ~ Bound Charge ~ Dark Matter ~ Scalar field
Predict Cosmology without further tuning
• Constraints: z=1010 (BBN) tBBN = 1sec initial cond.
z=1100 (CMB) Horizon 1 degree
z=0 (LRR) Gravity varies <4x10-13 yr-1
Match D(z) without Λ nor CDM!
Dielectric s ~ dφ/dt a0 , a0 ~ 1/2
Matching Horizon, Distance,
H0, BBN, … (Zhao et al. 06)
Falsifiable Beyond d /d R
• d /d Z – Vertical oscillation of Sun-like stars
• d2/d R2
– Roche Lobes of star clusters & dwarf galaxies
• d /d t – Hubble expansion/CMB/structure formation
A baryonic TeVeS is incomplete
• Fail in – Globular clusters (zero DM) – Galaxy clusters (lots of DM, e.g., 1 ev neutrino)
– Some lenses elliptical galaxies (with DM core)
• Falsifiable from vertical force near Sun (GAIA).
Lensing as usual, but
in strong regime
Compare with CDM
• Smaller image separation< 0.3 (GM/a0)1/2~ 3 kpc for M~1011
• Longer time delay (or need H0 closer to 70):
Lensing angle distribution in TeVeS
Chen & Zhao (2006, ApJ, Lett. submitted)
Not PerfectZhao, Bacon, Taylor, Horne (2006,MNRAS)
Skordis et al. (2005),PRL
• Fit WMAP,SDSSif neutrino is massive (~0.17)(← first peak location)
MOND as fortune-teller to DM/DE
• Why/When it works? – Often (LSB/SNIa) – but not always (globular/galaxy clusters)!
• E.g., Hydrogen Balmer Line = (1/22 - 1/n2) R leads to new physics: quantum/duality concepts of particle/wave
• (gDM /gDM ).gDM ~ a0 ~ ½ clues to DM/DE, even better physics [duality of gravity?]
• All structures in universe are characterized by the same internal energy density . Why?
Why gravity = a0 somewhere in
every object?
• GlobularCluster, MolecularCloud, dwarf, Ellip, X-Cluster
– ½ ~ a0 ~ Velocity2 /Length scale ~ cH0/6 ~ 100Msun/pc2
• A good theory (DM/DE/MOND…) should explain this!
Update Scores LCDM
TeVeS-MOND• Solar System ?
?
• Tides/vertical force
• Rot. curves HSB/LSB • Lensing by Ellip/Clusters
• Hubble Expansion/CMB ????
Stay Tuned!
Cluster Masses from X-rays
MOND says from velocity dispersion MTotal / MGas. ~ 2Need 2 eV neutrinos in clusters of galaxies.
Sanders & McGaugh: http://cul.arxiv.org/pdf/astro-ph/0204521
Neutrino Mass Limits
Maybe MOND + the galactic cluster results are the first measurement that the typical neutrino mass is ~2 eV ! (G.Godfrey 2006)
Mνe< 2.2 eV Tritium decay endpoint measurements (But much better will come from KATRIN ~2007). A much lower mass limit
would rule out neutrinos being a significant DM mass in galactic clusters.
Mνµ< 170 KeV π+ → µ+ + νµ
Mντ< 18 MeV τ - → 2 π - + π+ + ντ
(Mνe + Mνµ + Mντ) < .68 eV WMAP (March 2006 results for 3 years of data), but uses Einstein’s Field Eqn. for structure
formation (ie: Newton, which is not the MOND force law).
Fit Non-spherical Lens with Shear
Shan & Zhao (in prep.)
Disk Lens J2004-1349 H0 ~ (R2
2 -R12 ) (1-k)/ (t2-
t1) f(zs,zl) ~ 70
Toy Lens with 3-baryon centres
Kappa map
Density map
Angus, Famaey, Zhao (2006, MNRAS)
Duality of Gravity: DM-MOND
• Acceleration V2/R = -▼Φ = E
• Polarisation ▼ φ = P = D – E =
-▼Φlum + ▼Φ
Tracking▼. [s ▼ φ]= 4Glum
= ▼. ▼ Φlum
Dielectric s ~ ▼φ /a0 , a0 ~ 1/2 Baryon = Free
Charge
DM = Polarisation
Predict Cosmology …without further tuning
• CMB peaks: sensitive to baryon and dark matter
B h2 (shift of zero point of oscillation)
→ first peak height second peak height Mh2 (increases the depth of potential well decreases radiation relative to matter(ISW))
→ first peak height second peak → third peak height
• trouble with higher (second and third) peaks of CMB(Slosar-Melchiorri-Silk,2005)
(← Silk damping for baryons)WMAP
WMAP/Boomerang